a) Field of the Invention
The present invention relates to an optical system to be used with optical instruments and an optical module for carrying out stereoscopic photography, automatic focusing, etc. using the optical system.
b) Description of the Prior Art
In the recent years, there have been prevailing cameras for electronically picking up images such as those used in domestic video cameras, TV cameras, doorphones with cameras and so on. A great theme therefore lies in compact configuration and reduction of manufacturing costs of lens systems to be used in these cameras. A lens system which has a fixed focal length and is to be used in such a camera is generally composed of three to six lens elements.
For stereoscopic photography or automatic focusing, it is ordinarily required to use two optical systems, (left and right) or twice as many lens elements as are used in an ordinary lens system.
A lens system such as the conventional lens system described above which is composed of three to six lens elements uses a large number of lens elements and adopts a lens barrel which has a complicated structure to fix these lens elements, thereby requiring a high manufacturing cost. Further, such a lens system poses a problem that its performance is degraded due to eccentricities of individual lens elements produced at stages of working and assembly.
When two optical systems are required for stereoscopic photography, it is necessary to use two lens systems and accurately align these two lens systems.